This invention relates to magnetic recording media, and more particularly, to magnetic recording media having a rigid substrate plasma treated for improved bonding of a magnetic layer.
Several decades have passed since the appearance of megnetic recording media comprising a nonmagnetic substrate and a magnetic layer formed from a magnetic powder of oxide type such as gamma-Fe.sub.2 O.sub.3 and cobalt-containing gamma-Fe.sub.3 O.sub.4 and a binder. Recently, for the purpose of further improving recording density, magnetic recording media comprising a magnetic layer formed from a ferromagnetic powder such as Fe, Co, Ni, Fe-Co, Co-Ni, Fe-Co-Ni, Fe-Co-B, Fe-Co-Cr-B, Mn-Bi, MnAl, Fe-Co-V, etc. and a binder were developed and are now of great interest in the art.
Among these magnetic recording media there are known magnetic disks of the so-called hard disk type having a rigid substrate such as a metal substrate. The hard disks should have a high bond strength between their magnetic layer and substrate. The surface treatment of rigid substrates by any conventional process, for example, by corona discharge is not successful in achieving a sufficient bond strength.